1. Field of the Invention
This invention relates to a driving device, in particular for a proportioning pump of the piston-flowmeter type.
2. Description of the Prior Art
It is already a known practice to drive a proportioning pump by means of a positive-displacement machine which utilizes the energy of the main fluid stream into which an additive product to be measured is introduced. The disadvantage of this system, however, lies in the fact that its overall size and bulk become excessive whenever the process fluid has to pass through the meter at high flow rates.
In a known arrangement disclosed in particular in U.S. Pat. No. 3,053,435, a fluid motor serves to control a compressor for providing pressure compensation of a pressurized reservoir. The motor is constituted by a differential cylinder-piston assembly associated with a two-position four-way distributor, the changes of state of which are mechanically controlled by the moving system of the motor. This construction is complex, however, since it calls for the presence of an abutment for actuating the distributor beyond the distributor body, which is not conducive to small overall size of the device.
The device proposed in the present invention is similar to the system described in the patent cited in the foregoing except for the fact that the distributor control mechanism is entirely housed within the motor and is of much more simple design.